• 제목/요약/키워드: simulation growth function

검색결과 72건 처리시간 0.023초

양식선별효과에 관한 연구 (A Study on the Sorting Effect in Aquafarm)

  • 어윤양;송동효
    • 수산경영론집
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    • 제49권4호
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    • pp.19-36
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    • 2018
  • Overstock in aquaculture is a matter of concern in aquaculture management. To sort fish based on fingerling size in case of overstocking is an important problem in aquaculture farm. This study aims to determine the amount of fry overstock and sorting time in aquaculture farm. This study builds a mathematical model that finds the value of decision variables to optimize objective function summing up the fingerling purchasing cost, aquaculture farm operating cost and feeding cost under mortality and farming period constraints. The proposed mathematical model involves following biological and economical variables and coefficients: (1) number of fingerlings, (2) sorting time, (3) fish growth rate and variation, (4) mortality, (5) price of a fry (6) feeding cost, and (7) possible sorting periods. Numerical simulation is presented herein. The objective of numerical simulation is to provide decision makers to analyse and comprehend the proposed model. When extensive biological data about growth function of fry becomes available, the proposed model can be widely applicable to real aquaculture farms.

이온 질화에 의해 크롬 도금 층 위에 형성된 크롬 질화물의 성장에 관한 전산 모사 (Computer Simulation for the Growth of Cr-nitride Formed on Electroplated Cr during ion-Nitriding)

  • 엄지용;이병주;남기석;권식철;권혁상
    • 한국표면공학회지
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    • 제34권3호
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    • pp.231-239
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    • 2001
  • The structure and composition of Cr-nitrides formed on an electroplated hard Cr layer during an ionnitriding process was analyzed, and the growth kinetics of the Cr-nitrides was examined as a function of the ion-nitriding temperature and time in order to establish a computer simulation model prediction the growth behavior of the Cr-nitride layer. The Cr-nitrides formed during the ion-nitriding at $550~770^{\circ}C$ were composed of outer CrN and inner $Cr_2$N layers. A nitrogen diffusion model in the multi-layer based on fixed grid FDM (Finite Difference Method) was applied to simulate the growth kinetics of Cr-nitride layers. By measuring the thickness of each Cr-nitride layer as a function of the ion-nitriding temperature and time, the activation energy for growth of each Cr-nitride was determined; 82.26 KJ/mol for CrN and 83.36 Kj/mol for $Cr_2$N. Further, the nitrogen diffusion constant was determined in each layer; $9.70$\times$10^{-12}$ /$m^2$/s in CrN and $2.46$\times$10^{-12}$ $m^2$/s in $Cr_2$N. The simulation on the growth kinetics of Cr-nitride layers was in good agreements with the experimental results at 550~72$0^{\circ}C$.

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몬테카를로법을 이용한 고온 내압 요소의 크리프 균열성장 파손확률 평가 (Evaluation of Creep Crack Growth Failure Probability for High Temperature Pressurized Components Using Monte Carlo Simulation)

  • 이진상;윤기봉
    • 한국안전학회지
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    • 제21권1호
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    • pp.28-34
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    • 2006
  • A procedure of estimating failure probability is demonstrated for a pressurized pipe of CrMo steel used at $538^{\circ}C$. Probabilistic fracture mechanics were employed considering variations of pressure loading, material properties and geometry. Probability density functions of major material variables were determined by statistical analyses of implemented data obtained by previous experiments. Distributions of the major variables were reflected in Monte Carlo simulation and failure probability as a function of operating time was determined. The creep crack growth life assessed by conventional deterministic approach was shown to be conservative compared with those obtained by probabilistic one. Sensitivity analysis for each input variable was also conducted to understand the most influencing variables to the residual life analysis. Internal pressure, creep crack growth coefficient and creep coefficient were more sensitive to failure probability than other variables.

Molecular Dynamics Simulation Studies of a Model System for Liquid Crystals Consisting of Rodlike Molecules in NPT Ensemble

  • 이창준;심훈구;김운춘;이송희;박형숙
    • Bulletin of the Korean Chemical Society
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    • 제21권3호
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    • pp.310-316
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    • 2000
  • Molecular dynamics simulation studies for thermotropic liquid crystalline systems conposed of rodlike molecules with 6 Lennard-Jones interaction sites wre performed in NPT ensemble. Within the range of temperature studied, the system exhibited isotropic and smectic phase. For the characterization of the smectic phase, we examined the structure of the liquid crystalline phase via the radial distribution function, its longitudinal and transverse components to the director, and other orientational correlation function, its longitudinal and transverse components to the director, and other orientational correlation functions. In the smectic A phase, our results showed a large anisotropy in translational motion (i.e.,$D_⊥ >> D_∥$), and the decay of the collective orientational correlation function of rank two became slower than that of the single particle orientational correlation function of rank one. Comments on the spontaneous growth of orientational order directly from the isotropic phase are given.

Novel Phase States in Highly Charged Colloidal Suspensions

  • Terada Y.;Muramoto K.;Tokuyama M.
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
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    • pp.19-20
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    • 2003
  • Brownian-dynamics simulation on highly charged colloidal suspensions is performed by employing Tokuyama effective force recently proposed. The radial distribution function suggests that there exist three novel phases, a gas phase, a liquid droplet phase, and a face-centered cubic (FCC) crystal droplet phase, depending on the minimum values of that potential. The dynamics of droplet growth is also investigated both in liquid droplet phase and in crystal droplet phase. Thus, different types of characteristic growth stages are found.

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몬테카를로법을 이용한 비선형 확률계수모형의 추정 (Estimation Using Monte Carlo Methods in Nonlinear Random Coefficient Models)

  • 김성연
    • 한국시뮬레이션학회논문지
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    • 제10권3호
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    • pp.31-46
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    • 2001
  • Repeated measurements on units under different conditions are common in biological and biomedical studies. In a number of growth and pharmacokinetic studies, the relationship between the response and the covariates is assumed to be nonlinear in some unknown parameters and the form remains the same for all units. Nonlinear random coefficient models are used to analyze such repeated measurement data. Extended least squares methods are proposed in the literature for estimating the parameters of the model. However, neither objective function has closed form expression in practice. This paper proposes Monte Carlo methods to estimate the objective functions and the corresponding estimators. A simulation study that compare various methods is included.

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식물공장내 작물의 간격조절방법에 대한 식재면적지표 시뮬레이션 (Simulation of Planted Area Index (PAI) for Crop Spacing Methods in Plant Factory)

  • 김준용;양승환;이춘구;;이중용
    • Journal of Biosystems Engineering
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    • 제36권5호
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    • pp.348-354
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    • 2011
  • Various crop spacing methods have been implemented so far for the greenhouse and plant factory applications. However, there is no generally accepted parameter for evaluation of plant spacing efficiency in plant production system. In this study, 'Planted Area Index' (PAI) of a spacing method is defined as the ratio of the planted area in the field to required planted area using the spacing method when no transplanting operation is assumed. Three common types of spacing methods for plane placement of the plants were modeled mathematically. For calculating the planted area, an optimal growth radius function (R(t)) is needed. Function of the days after transplanting stage gives a radius of an optimal circle area for the living plants. A computer simulation was developed to calculate the PAI, based on three crop spacing methods and four optimal growth radius functions. In general, the 1-D zigzag spacing showed the best PAI. Moreover, it gives an example on how to apply the PAI for the design.

몬테카를로 모사에 의한 용접 계면에서의 크리프 균열성장 파손 확률 평가 (Evaluation of Creep Crack Growth Failure Probability at Weld Interface Using Monte Carlo Simulation)

  • 이진상;윤기봉
    • Journal of Welding and Joining
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    • 제23권6호
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    • pp.61-66
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    • 2005
  • A probabilistic approach for evaluating failure risk is suggested in this paper. Probabilistic fracture analyses were performed for a pressurized pipe of a Cr-Mo steel reflecting variation of material properties at high temperature. A crack was assumed to be located along the weld fusion line. Probability density functions of major variables were determined by statistical analyses of material creep and creep crack growth data measured by the previous experimental studies by authors. Distributions of these variables were implemented in Monte Carlo simulation of this study. As a fracture parameter for characterizing growth of a fusion line crack between two materials with different creep properties, $C_t$ normalized with $C^*$ was employed. And the elapsed time was also normalized with tT, Resultingly, failure probability as a function of operating time was evaluated fur various cases. Conventional deterministic life assessment result was turned out to be conservative compared with that of probabilistic result. Sensitivity analysis for each input variable was conducted to understand the most influencing variable to the analysis results. Internal pressure, creep crack growth coefficient and creep coefficient were more sensitive to failure probability than other variables.

화재시 열방출 급상승 구간의 수치모형 개발에 관한 연구 (로지스틱 함수 및 역함수 곡선) (Development of a Numerical Model for the Rapidly Increasing Heat Release Rate Period During Fires (Logistic function Curve, Inversed Logistic Function Curve))

  • 김종희;송준호;김건우;권오상;윤명오
    • 한국화재소방학회논문지
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    • 제33권6호
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    • pp.20-27
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    • 2019
  • 본 연구는 화재 시 열출력 급상승 구간에 대한 정확한 열방출율을 예측하기 위한 새로운 함수를 개발하여 제안하는 것을 목적으로 하였다. 현재 화재공학에서 사용되고 있는 'αt2' 곡선은 화재시스템 공학 관점에서 비효율적이며 실효성 저하를 초래하므로 열방출율의 예측오차를 최소화시킬 필요가 있다. 'αt2'과 비교하여 보다 논리적인 배경과 형태적으로 유사성을 가진 로지스틱 함수 이론을 기반으로 화재 급성장 구간은 물론 화재 초기 단계까지 적용 가능한 새로운 예측 함수를 개발하였다. 개발된 함수는 더 넓은 화재성장 구간에서 정확도 높은 예측결과를 갖는 것으로 본 연구에서 증명되었다. 이 연구결과는 향후 화재성장패턴 연구의 개발과 함께 화재공학의 발전을 위해 적용될 것이다.

육상수조 어류양식 생존율에 따른 비용분석모형 (Cost Analysis Model according to Mortality in Land-based Aquaculture)

  • 어윤양
    • 수산경영론집
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    • 제47권4호
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    • pp.1-13
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    • 2016
  • Fish mortality is the most important success factor in aquaculture management. To analyze the effect of mortality considering biological and economic condition is a important problem in land-based aquaculture. This study is aimed to analyze the effect of mortality for duration of cultivation in land-based aquaculture. This study builds the mathematical model that finds the value of decision variable to minimize cost that sums up the water pool usage cost, sorting cost, fingerling cost and feeding cost under critical standing corp constraint. The proposed mathematical model involves many aspects, both biological and economical: (1) number of fingerlings (2) timing and number of batch splitting event, based on (3) fish growth rate, (4) mortality, and (5) several farming expense. Numerical simulation model presented here in. The objective of numerical simulation is to provide for decision makers to analyse and comprehend the proposed model. When extensive biological and cost data become available, the proposed model can be widely applied to yield more accurate results.